1. Field of the Invention
The present invention relates to the field of automatic placement of electronic components on electronic circuits. More particularly, the present invention relates to a method and apparatus for supplying components to a placement machine.
2. The Prior Art
The automatic placement of electronic circuits (PCBs or similar) by means of placement machines has been known for some time and is used, in particular, whenever complex and extensive circuits are required to have a fairly large number of components placed on them quickly, efficiently, and without a large number of errors. The components in this process are sorted by type on individual tapes which are rolled on reels fed in steps, by means of a corresponding feeder, past a pickup position where they are picked up by a handling machine and placed in their allocated position in the circuit. In this process, the components are stored individually on the tape in pockets positioned periodically one after the other and are normally protected against falling or damage by an overlying cover tape. Such automatic placement devices are known, for example, from U.S. Pat. Nos. 4,610,083, 4,653,664, 5,191,693, 5,289,625 and 5,515,600, or from Japanese patent applications Japanese Patent Document Nos. A-05145283, A-02135800, A-03133763, and A-03008655.
If, in the operation of such a placement machine in the on-going placement process, more components of one type are needed than are stored on the corresponding tape reel, a new reel with a new tape has to be inserted in the feeder when the tape is drawing to an end. To do this, it is necessary to inform the operator when the end of the tape is reached so that corresponding actions can be initiated. Various solution proposals have already been made for this problem. For example, in Japanese Patent Document Nos. A-03008655, A-05145283, U.S. Pat. No. 4,653,664 or U.S. Pat. No. 5,191,693, the solution proposed was to apply different kinds of markings to the tape, in particular to the cover tape, which were then detected by a sensor positioned before or after the pick-up position and which gave a warning prior to this end of tape and simultaneously allowed an estimate or computation of the remaining utilization time of the inserted tape. Other proposals, such as those from Japanese Patent Document Nos. A-02135800 and A-03133763, use a coded sequence of empty and full pockets within the tape as the marking, the sequence corresponding at the output of the sensor to a certain bit pattern which can be processed in the control of the device.
Although the operator can prepare in good time for a coming tape replacement thanks to the prior warning or the prior display of the placement machine, the tape replacement itself requires an interruption in the placement process. The feeder is pulled out of its inserted position on the placement machine, the empty reel is replaced by a full reel with a new tape, the tape start of the new tape is threaded in and the feeder is reinserted in its inserted position on the placement machine. At the same time, the characteristic data (tape length, tape width, pitch, number of pockets or components, type of components) of the new tape has to be entered in the placement machine and activated so that the placement process can be continued in the standard manner. As a result of this, downtimes occur in placement which limit or reduce the placement performance of the whole unit.
It is therefore the object of the invention to provide a method for the supply of components in which a tape replacement can be performed without any loss in performance as well as a suitable feeder and placement machine for this method.
It is a further object of the present invention to provide for a splice sensor which allows an automatic and synchronous takeover of the relevant data (in particular component quantity) of the newly joined tape.
It is a further object of the present invention to provide for an empty pocket sensor which allows automatic control of the feeder and the placement machine with the evaluation of an empty-pocket code. The empty pocket code can then signal a batch end or a batch start on the tape.
It is a further object of the present invention to provide for a splice process which can be performed a synchronously during the placement process.
It is a further object of the present invention to prevent placement errors by splicing in a controlled manner by means of a barcode, where release for the joined tape is only given with an agreement of the data contents of the two barcodes (old/new tape), as well as for controlled and synchronous takeover of the relevant data of the joined tape such as: tape width, pitch, component identification/dimensions/values/quantity, process data, etc.
It is a further object of the present invention to provide for a programmable number of components per circuit which are guaranteed to be from the same batch are made available to the placement machine for mounting on a circuit.
It is a further object of the present invention to provide for no loss of placement performance by having the feeder controlled automatically, i.e. any insufficient quantity of components at the batch end is rejected and the feeder automatically advances to the next batch start.